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Think about what source of energy had the largest impact on the history of the automobile. Easy, right? It's gasoline.

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Not so fast. Though petroleum-based fuel was certainly a major player in the development and advancement of the car, it takes a back seat to another source of potential energy--electricity.
There is no denying that gasoline is responsible for the mechanical energy that moves a modern vehicle down the road, but without electricity, none of this could occur. You need electrical current to arc the spark plug; that begins the burn and the resulting expansion of the flame across the cylinder bore that drives the piston down and the crankshaft around.
But electricity is also used to make the car more user-friendly and enjoyable. Remember the days of hand-cranking the car to start it? The development of the electric starter motor was a major breakthrough--and spared drivers a lot of backbreaking work. Electric windshield wipers, too, were a great step forward when compared to either hand- or vacuum-operated models. Early drivers needed to move the wiper with a lever; later, when vacuum was applied, you'd often lose visibility on a long grade when the differential pressure in the engine became negated. Meanwhile, hot air from the engine coolant did little to warm the passenger compartment without an electric blower. And when electric bulbs replaced the carriage-inspired acetylene lamps that were so common in the old days, it became possible to drive safely at night. Safety measures made another great leap forward when electric turn signals and brake lamps were fitted to production vehicles. It's harder to imagine a vehicle without electrical power than one without gasoline.
Basic Electrical Theory
Electricity, because it cannot be seen, has always been shrouded in mystery. A simple fact is that electrical theory is just that--theory. Science has created a system of thought around empirical observations about the nature of electricity, then modified it each time some new fact arises. Observing these effects and fitting them together with observations on other areas of chemistry and physics led to the creation of atomic theory.
Matter is said to be composed of about 120 basic substances, called elements. They cannot be broken down any further without losing their identity. Some elements are copper, iron, gold, hydrogen, oxygen and helium. Each of these elements is made up of smaller parts called atoms.
An easy way to visualize atomic theory is as a tiny planetary system composed of particles held together by charges. Each atom is made up of a "planet" called the nucleus with one or more electrons in orbit around it, like moons. They are surrounded by a force field called an electrostatic field. Electrons have a negative field, while the nucleus has a positive field. The attraction between the positive and negative fields is what keeps the electrons from flying out of orbit.
Electric current is defined as the movement of electrons. As we all know, opposites attract--positive and negative move towards each other. An atom that has a strong positive charge--that contains a lot of protons in its nucleus--can tear orbiting electrons away from another atom. These electrons move towards the positive atom, and their movement creates a flow that we can harness to do work: electricity.
When working with electricity, there are two main measures: volts and amperes. To understand these concepts, it helps to compare electricity to water flow. The analogy isn't perfect, but it's useful.
Voltage can be considered electrical "pressure," while amperes, a measure of electron flow rate, is analogous to "gallons per minute." For electricity to perform work, you need a combination of pressure and flow, which is measured in watts: volts multiplied by amperes consumed equals watts.
A "conductor" is a material that allows electrical current to pass through it. In contrast, an "insulator" does not allow the free movement of electrons. George S. Ohm discovered opposition to electron flow in the early 1800s. He formulated a law that links the relationship of current flow and resistance in a base circuit. Ohm found that the current in a circuit is directly proportional to the applied voltage, and inversely proportional to resistance in the circuit. In other words, when resistance goes up or down, current goes up or down, assuming the voltage is the same. When voltage goes up or down, current flow goes up or down, assuming the resistance stays the same. When resistance goes up, current goes down (assuming the voltage stays the same). When resistance goes down, current goes up.
The basic knowledge of atomic theory, and the subset of that theory that governs the motion of electrons, along with Ohm's law allowed electricity to be harnessed for technological use, including in the automobile.
Electrical Components That Changed the Automobile
Electricity allowed the automobile to move from a dream to a reality. Many electrical devices were responsible for this evolution, but the storage battery, ignition system and electric motor may have been the most important.
Sometime around 1800, Alessandro Volta found that two different metals--copper and zinc-- would produce an electrical current if separated by moist paper. His "voltaic pile" produced about 2.2 volts and worked using a fluid or electrolyte that took electrons from one of the metal electrodes and deposited them on the other. In the production of electricity, the voltaic cell is consumed. For this reason, it's called a primary cell and cannot be recharged--it is destroyed by use.
An automobile's source of electrical power, in contrast, is called a storage battery. It operates much like a voltaic cell does, but it can be recharged, or put back into its original condition, for a certain number of times. This type of battery is made up of a series of two-volt storage cells called secondary cells. These cells are often called lead-acid cells, because these two materials were part of the construction of early storage batteries.
A storage battery can only withstand a fixed number of discharge and recharge cycles. Plates in a storage battery cell start out with opposite charges; one is positive and one is negative. As the cell discharges, the plates become more and more alike--their polarity decreases as electrons are supplied to the negative plate to replace those being drawn off into the circuit. Eventually, the plates degrade to a point where the storage battery can no longer supply any electrons. At that point, the battery is considered consumed and must be replaced.
The ignition system furnishes a spark to the correct cylinder at the proper time to ignite the fuel mixture. In early automobiles, ignition was triggered by a magneto. This was loosely based on a DC generator that produced an extremely high-voltage spark. The magneto was connected to a crude distributor that routed the spark to the correct plug at the right time. Usually, the vehicle had no storage battery or electrical system and the magneto was able to produce its own current.
When Ford introduced the Model T, an impressive eight-wire system served the ignition and the entire engine. A low-voltage magneto mounted on the front of the engine sent timed pulses to four coils on the firewall in a wooden box. The coils, each fitted with armatures and contact points, alternately opened and closed their own operating circuits, thus producing high-voltage secondary current. Four ignition cables routed the spark to the correct plugs. With the invention of a single point, single coil system and the adoption of the storage battery, the magneto was replaced with the precursor to our modern ignition system.
Meanwhile, the integration of an electric motor created what became known as the "self-starting car." An electric motor is created when a conductor carrying an electric current is placed in a magnetic field. The field conductor and the magnetic field interact with each other. The conductor tends to move away from the combined field and toward the weakened field. That is because the magnetic fields tend to aid one another on one side of the conductor and oppose each other on the other side. The conductor is pushed from one side and pulled from another. This is the basic principle of any electric motor, and is how the cranking motor or starter works.
Back to the Future
In the early 1900s, many vehicles powered solely by electricity were introduced. Many at the time believed that the electric car was a better concept than the internal combustion engine. The problem was that storage battery technology of the time could not provide a suitable range, and the time to recharge the battery was too long. In the end, the electric car succumbed to the gasoline engine.
But Detroit's dream of producing a commercially viable electric vehicle never died. In the late 1990s, General Motors offered the world's most advanced electric car to date, the EV1, in limited numbers and markets. This futuristic design offered excellent performance, but was too expensive to be sold in any significant numbers. Recent breakthroughs in battery technology have allowed for the three Detroit-based manufacturers to announce that electric cars will be in their showrooms by 2011. This time, it appears that the concept of an electric-powered automobile has finally arrived, and may very well be here to stay.

This article originally appeared in the April, 2010 issue of Hemmings Classic Car.